Many search engine services, such as GOOGLE and OVERTURE, provide for searching for information that is accessible via the Internet. These search engine services allow users to search for display pages, such as web pages, that may be of interest to users. After a user submits a search request (i.e., a query) that includes search terms, the search engine service identifies web pages that may be related to those search terms. To quickly identify related web pages, the search engine services may maintain a mapping of keywords to web pages. This mapping may be generated by “crawling” the web (i.e., the World Wide Web) to identify the keywords of each web page. To crawl the web, a search engine service may use a list of root web pages to identify all web pages that are accessible through those root web pages. The keywords of any particular web page can be identified using various well-known information retrieval techniques, such as identifying the words of a headline, the words supplied in the metadata of the web page, the words that are highlighted, and so on. The search engine service identifies web pages that may be related to the search request based on how well the keywords of a web page match the words of the query. The search engine service then displays to the user links to the identified web pages in an order that is based on a ranking that may be determined by their relevance to the query, popularity, importance, and/or some other measure. Three well-known techniques for determining importance or popularity of a page are PageRank, HITS (“Hyperlink-Induced Topic Search”), and DirectHIT.
Mobile devices, such as handheld personal computers, cell phones, and personal digital assistants (“PDAs”), are becoming increasingly popular ways to access the Internet. Unfortunately, the experience of users in accessing web pages using these mobile devices has been less than satisfactory. First, because these mobile devices have small display areas, it is difficult to effectively display in such a small display area a web page that is designed for a large display area. Second, because these mobile devices typically have a relatively slow communications link (e.g., via a cell phone network), it can take an unacceptably long time to download an accessed web page. Third, because the mobile devices have limited computing power, the rendering of a complex web page can also take an unacceptably long time.
Web page developers are currently attempting to create mobile-friendly pages taking into consideration the limitations of mobile devices. The W3C Mobile Web Initiative has published guidelines (“MWI Guidelines”) to make web pages more mobile-friendly. Although these “mobile-friendly” pages are not “mobile-specific” pages, that is, written in Wireless Markup Language (“WML”) or in Compact HTML (“cHTML”), they display and function well on mobile devices. Because the MWI Guidelines are not as strict as the limitations imposed by WML or cHTML, many web pages can satisfy the MWI Guidelines. As a result, the number of mobile-specific web pages is a small fraction of the number of mobile-friendly web pages. Since mobile search engines typically search only for mobile-specific pages, their search results can be less than satisfactory. General search engines typically do not treat mobile-friendly pages any differently than they treat other web pages. Since the number of mobile-friendly web pages is a small fraction of the total number of web pages, the web pages presented in search results of a general search engine are typically non-mobile-friendly and thus not suitable for display on a mobile device.
One technique has been described to assess mobile friendliness of web pages by applying various tests or rules to a web page. The technique then generates a weighted sum of the results of the tests to give an overall score of mobile friendliness. (MobiReady Report (Beta), “http://” followed by “mr.” then “dev.” and then “mobi”.) The scores of the web pages generated by this technique, however, do not accurately represent what a person would think is a mobile-friendly web page.
Some techniques have been developed to dynamically adapt web pages that are too large for a small display area. One such adaptation technique is “page splitting,” which attempts to divide a web page into blocks that can fit as a unit into a small display area. One such page-splitting technique analyzes the position and shape of HTML elements of a web page to identify blocks. However, it can be difficult to identify blocks from low-level HTML tags in a way that preserves page structure and does not lose information. An adaptive page is usually divided into many small pages, and the small pages are connected to each other through navigational links. As a result, it is difficult for mobile users to get a sense of the overall structure and organization of a web page by looking at one small page at a time.